As an exemplar of this type of operation control device, one may enumerate an operation control device for a hydraulic power shovel.
As well known, this type of power shovel is equipped with hydraulic cylinders as actuators, hydraulic motors, and operating levers. The hydraulic cylinders respectively provide necessary drive forces for working tools such as booms, arms and buckets. The hydraulic motors generate necessary drive forces for a traveling system and a revolving system of the power shovel. The operating levers, provided in association with the hydraulic actuators, are collectively installed in a cabin. For a specific operation of a working tool, an operator properly operates the operating levers with a required direction and a required stroke. The direction and stroke determine a drive direction and a drive amount of the related actuators, viz., an influx direction and a flow rate of the pressure oil (the control system is generally called a pilot operate system).
When operating the power shovel, an operator frequently uses a called multi-operation (to simultaneously supply pressure oil to a plurality of actuators in order to simultaneously drive different actuators, such as the combination of a boom and an arm, and the combination of an arm and a bucket, by simultaneously operating the corresponding operating levers. When the above operating control device is operated for effecting the multi-operation, the priority order for pressure oil to flow into the intended actuators depends on the current pressures in the load circuits connecting to the actuators. The flow rate of the pressure oil to each actuator depends on a stroke of the related lever by an operator.
Let us consider a case that the multi-operation is for the combination of a boom and an arm, and the boom must be operated earlier than the arm. In this case, if the boom load is lighter than the arm load at a time point, the pressure oil first enters the actuator associated with the boom. Therefore, this multi-operation is relatively easy. Reversely, if the boom load is heavier than the arm load, the pressure oil first enters the actuator associated with the arm. This makes the multi-operation complicated and difficult. In this case, to effect an intended work, an operator must actively operate the operating levers, generally two, associated with the boom and the arm, while adjusting the strokes. This lever operation requires highly skilled operators. Unskilled operators, if engaged upon such a multi-operation, consume much time and increase the cost for the working. The working finish is most frequently imperfect and unsatisfactory.
The above problems of the operations, particularly the multi-operation, also exist in any other operation control device not based on the pressure oil in which a plurality of actuators respectively associated with operating means such as levers are provided, and the drive amounts of the actuators are controlled by the strokes of the corresponding operating means, respectively. Also in those other operation control devices, the operation of the operating means is considerably complicated and difficult. A high-degree skill is required for intentionally controlling different actuators for the intended operations.
For the above background reasons, an object of the present invention is to improve the operability of this type of the operation control device, and to enable any operator including skilled and unskilled operators to exactly control the actuators in any operating mode including the multi-operation.